DE 36 24 481 discloses a device in which conveying of the item to be treated and the electrical contacting accomplished by clamps arranged adjacent to one another in a series on a continuously revolving drive belt. The clamps grip the item to be treated at the start of the conveyance path by being brought from an open state into a closed state, thereby simultaneously producing the required electrical contact to the item to be treated. At the end of the conveyance path, the clamps are respectively brought from the closed into the open state in order to re-release the item to be treated. Conventionally, the item to be treated is conventionally gripped and contacted on the conveyance path by a plurality of adjacent clamps simultaneously.
In this known device for conveying a flat item to be treated, the clamps are configured in such a way that a first clamp half having a first clamping surface is arranged below the conveyance plane so as not to be movable with respect to the conveyance plane. A second clamp half having a second clamping surface is arranged above the conveyance plane and is movable with respect to the conveyance plane. The movement of the second clamp half in the direction of the conveyance plane, in order to bring the clamp into the closed state, is produced by a resilient force. The reverse movement, to bring the clamp from the closed into the open state, takes place counter to the resilient force in that a portion rigidly connected to the second clamp half is guided via a ramp fixed along the conveyance path, thus causing an overall upward movement of the second clamp half and the second clamping surface.
However, in this known arrangement, there are problems with respect to the introduction of the item to be treated between the lower clamping surface and the upper clamping surface. As the lower clamping surface is fixed with respect to the conveyance plane, it is flush with the conveyance plane. In order to prevent the item to be treated from abutting or becoming scratched by an edge of the lower clamping surface during introduction between the lower clamping surface and the upper clamping surface, it is necessary for the item to be treated to be raised out of the conveyance path and then introduced between the lower clamping surface and the upper clamping surface. This may take place, for example, using a ramp arranged in the introduction region. However, this procedure is problematic, in particular in the case of very thin printed circuit boards and conductor foils, as, at the moment of clamping, the item to be treated is not located in the conveyance plane, thus causing stretching, compression or another form of distortion of the item to be treated. In addition, this problem is further intensified by flow effects in the electrolytic solution, as a result of which in particular thin items to be treated are deformed and deflected from the intended conveyance plane, so the deflection caused by the ramp must accordingly be increased in order to allow reliable introduction of the item to be treated between the clamping surfaces.
Owing to the subsequent electrolytic treatment or the deposition of additional material on the item to be treated, deformations are generally no longer reversible, and unacceptable alignment imprecision during subsequent processing steps, and therefore rejection, occurs. Moreover, scratching may occur in the output region of the device, i.e., during opening of the clamp and subsequent forwarding, on the side of the clamp half arranged so as not to be movable with respect to the conveyance plane, i.e. on the lower side of the item to be treated, and this may also result in an increased rejection rate.
WO 99/10568 describes the protection of clamps using a plastics material cover in order to reduce the deposition of material on the clamps.